Hi,
I'll chime in with....,
First, I'm running a Jacobs CD box, an OEM dizzy with a Pertronix. My plugs are Autolite 3924s. Gapped at .045". These are the small base plugs in TW heads.
Nothing exotic, they burn clean and have been working well.

I have always run autolites in my in-line 6 nothing fancy just standard autolite plugs...I am interested in what others are using in their I-6 especially if any are using some of the proclaimed higher efficiency plugs.

I switched to the petronix electronic ignition several years back I love it No more point replacement or adjustments! I have seen mixed reviews on Petronix but my experience has been good...

I also put in a more modern coil pretty sure I used a Accel super stack model I believe it helped my idle

Autolite plugs have always been the best in my car and they are also the most economical. I run a set of plugs for two years on my daily driver (classic) with no perceptably reduction in performance. When I change them the gap is around .040" which means it has grown .012" in the two years. (Yes I gap my plugs at .028" - it works best for me) The plugs cost right around a dollar each. You don't get that kind of service out of any other plug on a daily driver - not that I have ever seen anyway.

1966 Coupe 351WTop Loaderrebuilt, rewired, modified for slalom and hill climbNo racing - just a fun car built by and for me.Project in process

Autolite plugs have always been the best in my car and they are also the most economical. I run a set of plugs for two years on my daily driver (classic) with no perceptably reduction in performance. When I change them the gap is around .040" which means it has grown .012" in the two years. (Yes I gap my plugs at .028" - it works best for me) The plugs cost right around a dollar each. You don't get that kind of service out of any other plug on a daily driver - not that I have ever seen anyway.

That's interesting. .012" is a huge differance; almost 50%. Especially in only 2 years. That means your spark is so hot, that it's melting away the electrodes - eating them up.

I think there's a reason that no manufacturer that I know of recommends a gap so small.

But, I do agree that standard Autolite copper cores are the best bang for the buck.

There are engines that won't run with plug gaps larger than .022" - I think its a Mitsubishi 4 cylinder - carbureted. but there are others. When I used to race we would reduce the plug gap until we got a rough idle and then increase it until the idle smoothed out. That made the spark stonger all the way up in the rpm range. It also keeps the voltage down so wires last longer. The best reason for the small gap is (with points ignition) that the amperage goes up the same percentage that the voltage goes down. That amperage is heat - and heat ignites your fuel - not voltage! The spark won't have any difficulty with the turbulance "blowing the spark out" with small gaps. I get 21 mpg with my 302 C4 with 100000+ miles. The more compression you have the more important this is.
Modern electronic ignitions use an amplifier that increases amperage and voltage rise so it is less important to have a small gap. Even at that, small gaps never hurt - and they will still reduce your voltage so your plug wires will last longer than with a wide gap.

1966 Coupe 351WTop Loaderrebuilt, rewired, modified for slalom and hill climbNo racing - just a fun car built by and for me.Project in process

What's the difference between a resister plug and a non-resister plug (other than one having a higher resistance, of course) and which is best for a stock ignition?

If you like to listen to your stereo/radio without having it buzz in relation to your engine rpm, resistor plugs are better. Non-resistor plugs are for cars without radios or guys who use the buzz as a tach.

1966 Coupe 351WTop Loaderrebuilt, rewired, modified for slalom and hill climbNo racing - just a fun car built by and for me.Project in process